Filament tensioning device



Dec. 1, .1959 c. M. GARRETSON 2,915,663

FILAMENT TENSIONING DEVICE Filed Jan. 14, 1955 3/ 3/ 3/ gig INVENTOR CRAIG M. GARREZSON ATTORNEY 1 2,915,668 FILAMENT rnNsmNINo nnvrcn Craig M. Garretson, Jackson Heights, N.Y., assignor, by mesne assignments, to Syivania Eiectric Froducts 111C. Wilmington, DeL, a corporation of Delaware Application .lanuary 14, 1955, Serial No. 481,824 11 Claims. (Cl. 313-278) This invention relates to electron discharge devices, and more particularly to the structure of, and method for making filament tension supports for such devices.

In an electron tube having a filamentary cathode, means are provided for tensioning the filament so as to eliminate objectionable microphonics when the tube is subjected to shock or vibration. *In addition, the tensioning means prevents sagging of the filament when heated, thus reducing the probability of shorting the cathode with other electrodes within the tube.

A known construction of a filamentary tensioning structure comprises a support bar having a U-shaped tension spring wound thereon, and a bracket securely attached to the support bar for rigidly positioning the otherwise free ends of the spring. In this type of tensioning structure, the spring is wound upon its support bar, and is held in position while the two ends of the spring are welded to the bracket.

It is desirable, especially in subminiature tubes, to eliminate complex structures, and to provide for simple and uniform methods for constructing the constituent elements. The structures and methods of this invention increase the performance characteristics, reliability, and uniformity of the finished tubes.

Accordingly, an object of the invention is to provide for an improved filament tensioning device which is compact and simple in structure.

A further object of this invention is to provide for an improved method for making filament tensioning devices which is adaptable for automatic production of the devices.

A still further object of this invention is to provide for an electron discharge device which has improved electrical operating characteristics and less chance for mechanical failures, such as open welds.

Further objects of this invention will be apparent from the following detailed description, considered in connection with the accompanying drawings. These features of the invention which are novel and patentable are enumerated in the claims appended hereto.

Fig. 1 is a cross-sectional view of an electron tube embodying one form of the invention, parts being broken away to expose inner portions of the electron device.

Fig. 2 is a perspective view showing the association of the spring device with the rest of the mount, the filament being under tension.

Fig. 3 shows a bar of indefinite length utilized to support a number of tension springs.

Fig. 4 shows a fragment of the bar with notches therein.

Fig. 5 shows the same fragment in association with a spring to be fastened thereto.

Fig. 6 shows one end of the spring lying in a notch in the bar.

Fig. 7 shows the spring when secured to the bar.

Fig. 8 is a view showing the bar with its springs divided up into individual units forming the finished product to be utilized in a radio tube.

Fig. 9 is a modification wherein the spring is wound several turns around the bar after the ends of the spring wire had been secured to the bar.

Referring to Fig. 1, the electron tube comprises an envelope 13 within which is mounted an electrode assembly 15 and envelope leads 17. The electrode assembly 7 2,915,668 Patented Dec. 1, 1959 15 has an anode 19 welded to anode supports 21 anchored in the envelope and which may be prolongations of two of the leads 17, a split frame grid 23 secured between pairs of insulated metallic grid support and anode spacing rods 25, and a filamentary cathode 27 which is held under tension and in proper alignment with the grid 23 by means of a tensioning device 29 on one end, and tab 18 secured to one of the leads 1'7 on the other. The grid frame is further supported by a prolongation 37 thereof being welded to another lead 17 The tensioning device 29 comprises a bar 31 having a resilient wire member 33 fastened thereto. This resilient member has an intermediate, substantially U-shaped section 34 and terminal portions 36 which may or may not be wound about the bar. The tensioning device 29 is mounted close to and above the electrode assembly 15 by means of Weld connections of two of the rods 25 with the bar 31. The free ends of portions 36 are embedded in notches 39 in the bar by means of a notching and peening operation, as will be described. The bar 31 is attached to the rods 25 as close to the anode and grid as feasible to thereby reduce the length of the filament 27, the rods for this purpose being stripped of insulation at their ends.

The proper voltages are applied to the anode 19 and grid 23 by means of their respective leads 17. One side of the filament electrical supply is connected to the fila ment via tab 18 through one of the leads 1'7, and the other side of the supply is connected to the filament through another lead 17 via a tab 41, an insulated rod 25, bar

31, and resilient member 33. The insulation on the upper and lower ends of the insulated rods 25 is removed to facilitate welding the bar 31 to the rods 25, and to provide for the filament electrical connection.

Figures 3 through 8 illustrate the method of making one type of tension device. A bar 31, illustrated in Figure 3, is notched at predetermined positions, as at 39 in Figure 4, by any suitable wedge-shaped tool. Into the openings in the notches is looped, somewhat sinusoidally, a resilient wire 33 to form loops 34- and 35 above and below the rod, the loops 34 above the rod being of larger amplitude than those below the rod, as shown in Figure 5. The wire lies in the notches, as shown in Fig. 6. By means of a peening tool, the material at the edges of the notches 39 is forced over the wire 33, as shown in Figure 7, thereby securing the wire to bar 31. During the peening operation, or subsequently thereto, the lower smaller loops may be cut off.

Next the bar with the loops afiixed thereto is cut apart to form individual spring units as shown in Fig. 8.

Previously, if desired, the U-shaped wire may have been wound about the longitudinal axis of rod 31 one or more times to form a tension device as shown in Figure 9. The wire 33 is stressed so that it will resiliently retain the coiled shape.

vFilamentary t'ensioning devices made in accordance with the invention can be made easily, uniformly, and inexpensively. In addition, an electron tube utilizing this tension device has less chance for mechanical failures than tubes of the prior are since it requires only two welds to connect the support wire 33 to the rods 25 instead of the four welds needed in currently made tubes. Furthermore, the tube will give a better performance electrically, since the tensioning device, because of the absence of the bracket of the prior art, can be mounted closer to the electrode assembly. This smaller structure facilitates the use of a shorter filament, which requires less power and has a higher resonant frequency. Also, with the use of a shorter filament, there will be less filament coating exposed above the electrode assembly, thereby reducing stray emission and undesirable effects such as noise.

Although specific embodiments of the invention have been shown and described, it will be understood that modifications may be made therein Without departing from the scope and spirit of the invention as defined in the appended claims.

What is claimed is:

1. An electron discharge device comprising a grid, an anode, a filamentary cathode, a tensioning device, and insulated electrode support rods spacing apart said grid and anode, said tensioning device being affixed to the rods to position the device in close proximity to the grid and anode, the tensioning device having a bar and a resilient member, said resilient member comprising a curvilinear portion and terminal portions, the terminal portions being attached to the bar, with the bar attached to the rods, and said filamentary cathode being supported by the curvilinear portion.

2. An electron discharge device comprising a grid, an anode, a filamentary cathode, a tensioning device, and insulated electrode support rods spacing apart the grid and anode, said tensioning device being afiixed to the rods to position the device in close proximity to the grid and anode, the tensioning device having a notched bar and a resilient member, said resilient member comprising a curvilinear portion and terminal portions, the terminal portions being embedded in the notches in said bar, with the bar secured to the rods, and said filamentary cathode being supported by the curvilinear portion.

3. An electron discharge device comprising a grid, an anode, a filamentary cathode, a tensioning device, and insulated electrode support rods spacing apart the grid and anode, said tensioning device being afiixed to the rods to position the device in close proximity to the grid and anode, the tensioning device having a bar and a resilient member, said resilient member having an intermediate curvilinear portion and terminal portions comprising helical coils, with the ends of the coils attached to the bar, with the bar attached to the rods and said filamentary cathode being supported by the curvilinear portion.

4. An electron discharge device comprising a grid, an anode, a filamentary cathode, a tensioning device, and insulated electrode support rods spacing apart the grid and anode, said tensioning device being afiixed to the rods to position the device in close proximity to the grid and anode, the tensioning device having a notched support bar and a resilient member, said resilient member having an intermediate curvilinear portion and terminal portions, the terminal portions comprising helical coils, the ends of which are embedded in the notches in the bar, with the bar attached to the rods, and said filamentary cathode being supported by the curvilinear portion.

5. An electron discharge device comprising a grid, an anode, a filamentary cathode having an electrical connector, stem leads, a tensioning device, and insulated electrode support rods spacing apart the grid and anode, said support rods having afilxed thereto the tensioning device for positioning it in close proximity to the anode, the tensioning device having a bar and a resilient member, said resilient member comprising a curvilinear portion and terminal portions, the terminal portions being attached to the bar, said filamentary cathode being supported and aligned by the curvilinear portion and in electrical contact therewith, one of said rods being in contact with one of said stem leads.

6. A method of making a tensioning device for a filamentary type cathode including the steps of notching a bar at spaced intervals, lacing a resilient Wire across the bar to form a series of loose turns, successive turns extending from the bar in opposite directions, with the ends of said turns disposed in the notches in said bar, closing the notches in the bar over the ends of the turns, removing all of the turns extending from the bar in a same direction, and severing the bar intermediate the remaining loose turns.

7. -A method of making a tensioning device for a filamentary type cathode including the steps of notching a bar at spaced intervals, lacing a resilient Wire across the bar to form a series of loose turns, successive turns extending from the bar in opposite directions, with the ends of said turns disposed in the notches in said bar, closing the notches in the bar over the ends of the turns, removing all of the turns extending from the bar in a same direction, and severing the rod intermediate the remaining loose turns.

8. A method of making a tensioning device for a filamentary type cathode including the steps of notching a rod at spaced intervals, lacing a resilient Wire across the rod to form a series of loose turns, with the ends of the loose turns being disposed in the notches in said rod, closing the notches in the rod over the ends of the loose turns, removing some of the turns, wrapping a portion of the remaining loose turns around the rod to form several tight turns on both sides of each remaining loose turn, and severing the rod intermediate adjacent Wrapped portions of the loose turns.

9. A method of making a tensioning device for a filamentary type cathode including the steps of notching a rod at spaced intervals, lacing a resilient Wire across the rod to form a series of loose turns, with the ends of the loose turns being disposed in the notches in said rod, closing the notches in the rod over the ends of the loose turns, removing some of the loose turns, wrapping a portion of the remaining loose turns around the rod to form several tight turns on both sides of each remaining loose turn, and severing said rod intermediate said remaining loose turns.

10. A method of making a tensioning device for a filamentary type cathode including the steps of notching a rod at spaced intervals, lacing a resilient wire across the rod to form a series of loose turns, every other turn extending from the rod in opposite directions, with the ends of the loose turns being disposed in the notches in said rod, closing the notches in the rod over the ends of the loose turns, removing all of the loose turns extending from the rod in a same direction, Wrapping a portion of the remaining loose turns around the rod to form several tight turns, and severing said rod intermediate said remaining loose turns.

11. A method of making a tensioning device for a filamentary type cathode including the steps of notching a rod at spaced intervals, lacing a resilient wire across the rod to form a series of loose turns, every other turn extending from the rod in opposite directions, with the ends of the loose turns being disposed in the notches in said rod, closing the notches in the rod over the ends of the loose turns, removing all of the loose turns extending from the rod in a same direction, wrapping a portion of the remaining loose turns around the rod to form several tight turns on both sides of each remaining loose turn, and severing said rod intermediate said remaining loose turns.

References Cited in the file of this patent UNITED STATES PATENTS 780,586 Thurston Jan. 24, 1905 1,926,128 Steenis Sept. 12, 1933 2,068,628 Kronenwetter et al Jan. 19, 1937 2,176,918 Narwid Oct. 24, 1939 2,181,288 Washburn Nov. 28, 1939 2,412,800 Curtis Dec. 17, 1946 2,467,390 Kelley Apr. 9, 1949 2,480,608 Rangabe Aug. 30, 1949 2,506,895 Sassaman et al May 9, 1950 2,672,570 Carlstrom Mar. 16, 1954 2,728,017 Haas Dec. 20, 1955 2,770,753 Moesker Nov. 13, 1956 FOREIGN PATENTS 265,973 Great Britain Aug. 4, 1927 

